Monitoring prostate thermal therapy with diffusion-weighted MRI

Department of Electrical Engineering, Stanford University, Stanford, California 94305-5488, USA.
Magnetic Resonance in Medicine (Impact Factor: 3.57). 06/2008; 59(6):1365-72. DOI: 10.1002/mrm.21589
Source: PubMed


For MR-guided minimally invasive therapies, it is important to have a repeatable and reliable tissue viability evaluation method. The use of diffusion-weighted MRI (DWI) to evaluate tissue damage was assessed in 19 canine prostates with cryoablation or high-intensity ultrasound (HIU) ablation. The apparent diffusion coefficient (ADC) trace value was measured in the treated tissue immediately upon the procedure and on the posttreatment follow-up. For the acute lesions, the ADC value decreased to (1.05+/-0.25)x10(-3) mm2/s, as compared to (1.64+/-0.24)x10(-3) mm2/s before the treatment. There was no statistical difference between previously frozen or previously ultrasound-heated lesions in terms of the 36% ADC reduction (P=0.66). The ADC decrease occurred early during the course of the treatment, which appears to complicate DWI-based thermometry. Over time, the ADC value increased as the tissue recovered and regenerated. This study shows that DWI could be a promising method to monitor prostate thermal therapies and to provide insight on tissue damage and tissue remodeling after injury.

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    • "Success of MRI temperature monitoring depends on the accuracy of temperature estimation. Out of a variety of different approaches, including proton density, T1 and T2 relaxation times, diffusion coefficient, and magnetization transfer, the proton resonance frequency shift (PRFS) method is the only one that offers a linear relationship to temperature and low susceptibility to tissue quality [12-21]. All MR thermometry models in common are in a state of quality assessment and rely on animal or ex vivo models. "
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    ABSTRACT: To compare the accuracy of a semi-quantitative proton resonance frequency shift (PRFS) thermal mapping interface and an alternative qualitative T1 thermometry model in predicting tissue necrosis in an established routine setting of MRI-guided laser ablation in the human liver. 34 cases of PRFS-guided (GRE) laser ablation were retrospectively matched with 34 cases from an earlier patient population of 73 individuals being monitored through T1 magnitude image evaluation (FLASH 2D). The model-specific real-time estimation of necrotizing thermal impact (above 54 °C zone and T1 signal loss, respectively) was correlated in size with the resulting necrosis as shown by lack of enhancement on the first-day contrast exam (T1). Matched groups were compared using the Mann-Whitney test. Online PRFS guidance was available in 33 of 34 cases. Positive size correlation between calculated impact zone and contrast defect at first day was evident in both groups (p < 0.0004). The predictive error estimating necrosis was median 21 % (range 1 % - 52 %) in the PRFS group and 61 % (range 22 - 84 %) in the T1 magnitude group. Differences in estimating lethal impact were significant (p = 0.004), whereas the real extent of therapy-induced necrosis showed no significant difference (p > 0.28) between the two groups. PRFS thermometry is feasible in a clinical setting of thermal hepatic tumor ablation. As an interference-free MR-tool for online therapy monitoring its accuracy to predict tissue necrosis is superior to a competing model of thermally induced alteration of the T1 magnitude signal.
    PLoS ONE 10/2013; 8(10):e78559. DOI:10.1371/journal.pone.0078559 · 3.23 Impact Factor
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    ABSTRACT: MR guidance of high intensity focused ultrasound is evolving with each new application. In this paper we describe ongoing research in the MR-guidance aspect of MR-guided focused ultrasound. The structure is divided into the pretreatment/setup phase of the procedure, MR thermometry for monitoring the actual treatment, and methods for assessment and follow-up.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:141-4. DOI:10.1109/IEMBS.2009.5334680
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